Effects of abomasal oligofructose on blood and feces of Holstein steers.

Subacute ruminal acidosis can result in increased flow of fermentable substrates to the hindgut, which can negatively affect animal health and productivity. However, animal responses to increased hindgut fermentation independent of subacute ruminal acidosis have rarely been evaluated. This study determined the impact of abomasal dosage of a fermentable carbohydrate on animal performance and blood and fecal variables. Six ruminally cannulated Holstein steers fed a lactating dairy cow ration were used in a crossover design study with 14-d periods. On d 13 of each period, steers were infused abomasally with a pulse dose of 0 (control) or 1 (Oligo) g of oligofructose/kg of BW. Blood samples collected at 0, 3, 6, 9, 12, and 24 h after abomasal oligofructose dose were evaluated for metabolites (blood urea N, β-hydroxybutyric acid, and NEFA) and systemic inflammatory markers (Cu, serum amyloid A, and haptoglobin). Fecal samples, rectal temperature, heart rate, and respiratory rate were taken at 0, 3, 6, 9, 12, 24, and 48 h after abomasal dosage. Fecal samples were assayed for pH, DM percentage, consistency score (1=liquid to 5=coarse), and organic acid concentrations. Data were evaluated using a model including the fixed effects of treatment, time after dosage, and their interaction. Effects of treatment or treatment × time were not significant for DMI, blood variables, rectal temperature, or respiratory rate. Fecal pH was slightly reduced for Oligo compared with control steers (6.76 vs. 7.02; P=0.04). A treatment × time interaction occurred for fecal DM (P < 0.001). Compared with control steers, DM content of feces was reduced in Oligo steers at 6 h (12.6 vs. 15.2%) but increased at 9 h (16.3 vs. 15.0%) and 12 h (16.5 vs. 15.0). Fecal consistency score was reduced by the Oligo treatment at 6 h (1.44 vs. 2.83; P < 0.001) and 9 h (1.83 vs. 2.67; P=0.005). A treatment × time interaction was detected for fecal concentrations of lactate and acetate (P < 0.05) and tended to occur for propionate and butyrate (P < 0.10). The greatest difference for all organic acids occurred at 12 h, when fecal concentrations of lactate, acetate, propionate, and butyrate were 0.5, 47, 11, and 4.0 mM in control steers and 5.3, 76, 15, and 6.8 mM in Oligo steers, respectively. In summary, abomasal dosage of 1 g of oligofructose/kg of BW increased fecal excretion of microbial fermentation products in steers without causing metabolic acidosis, metabolic disruption, or inflammation.